1. Field of the Invention
The invention is directed to a weaving machine with a device for forming a shed from work threads, with weft thread insertion means for the insertion of a weft thread into the shed with guide elements for the weft thread insertion means, wherein the guide elements can move into and out of the shed, and with a weaving reed containing weaving reed dents for beating up an inserted weft thread at the knock-off of a woven fabric to be produced.
The weft thread insertion means feature is understood and referred to herein in its broadest meaning, e.g., such means as projectiles, grippers, shuttle, air jet or other media for insertion of a weft thread into a shed formed of warp threads. A great number of such weft thread insertion means are likewise known.
2. Description of the Related Art
Weaving machines of the type mentioned above are often high-power weaving machines in which the weft thread insertion means move into and out of the shed. Guide elements are required for this purpose, wherein difficulties arise in the processing of warp threads formed of parallel yarns. Parallel yarns are formed of a plurality of (at least two) individual synthetic fibrils or fibers which extend parallel to one another with practically no twisting. To prevent the fibrils of these threads from coming apart, they are glued together by paste or size or are connected portion-by-portion by an air interlacing or intermingling process. Yarns that have been produced by air interlacing are called air-interlaced or air-entangled yarn. There is a tendency for the warp threads made from such parallel yarns to split up at the guide elements, resulting in fibril breakage and/or thread breakage. This drastically reduces the efficiency of such high-power weaving machines, so that, ultimately, rather than such parallel yarns, only expensive twisted yarns can be used in these machines. In order to remedy this somewhat, such parallel yarns are additionally provided with a paste or size. Apart from the fact that such sizing processes are expensive, the size causes very extensive soiling of the weaving machines. Further, the size must be washed out during further processing of the woven fabric. The washed out size must be disposed of in an environmentally sound manner by a very cost-intensive process.
A shuttleless weaving machine is known from FR-A-2 547 602, wherein, in order to avoid the above-mentioned disadvantages, guide elements are formed at every reed dent to form an insertion channel in order that a weft thread can be introduced by means of air jets. However, this cannot prevent the risk of warp threads of untwisted yarn remaining suspended at the blowing nozzles or air jet nozzles, because these nozzles are wider than the spacing between the reed dents and accordingly than the spacing between the warp threads, and the latter are forced apart by the air jet nozzles during the swiveling of the weaving reed. Since the thickness of the guide elements only corresponds to the thickness of the reed dent, the guide elements are very thin and do not have sufficient stability and can bend, thereby increasing the risk that parts of the warp thread will remain suspended. They are not at all suitable for guiding the weft insertion members. In order to achieve adequate stability, the reed dents, and accordingly the guide elements, would have to be thicker, so that only a very coarse pitch of the weaving reed dents would be possible and only a correspondingly coarse woven fabric could be manufactured.
DE-U-91 00 753 discloses a weaving machine in which the weaving reed is provided with a shuttle guide whose going-parts having sliding elements which extend in the direction of the warp threads and engage between the warp threads. The sliding elements are wider than the warp thread spacing. In front of or behind every sliding element, there is arranged a displacing element which has at least the same width as the sliding element, but has a greater height than the sliding element and forms a dent bar or gap between the warp threads. The displacing element forms a point at the free end. The displacing element must force the warp threads apart with every change of shed to form a gap. This shuttle guide can not overcome the problems described above because it is suitable only for high-quality twisted yarns, but not for parallel yarns which would be damaged or destroyed at the pointed displacing element.